A small cell network (SCN) is considered as an effective means to deal with rapid increasing of data traffic. Due to dense deployment of small cells, synchronization signals and reference signals will be interfered severely among cells. Therefore, it needs to solve the problem of performing radio resource management (RRM) measurement on the reference signal in the small cell scene. In addition, in order to deal with blowout growth of the data traffic in the future, an operator may deploy more small cells so as to utilize all available spectrum resources as much as possible. Some unlicensed frequency bands for example a 5 GHz frequency band have rich spectrum resources, and effective utilizing of these frequency bands may assist the operator to provide faster and better services. However, introducing of a long term evolution-unlicensed (LTE-U) frequency band or a Licensed-Assisted Access (LAA) frequency band further increases the interference among the small cells, thereby further intensifying the problem of RRM measurement for the reference signal.
On the other hand, presently RAN 1 is discussing an ON/OFF mechanism of the small cell. In addition, the RAN 1 designs a new reference signal, i.e., a discovery reference signal (DRS), to support an ON/OFF process of the small cell. The DRS-based measurement facilitates the subsequent ON/OFF of the cell and user switch. Due to new characteristics of the DRS, the RRM measurement based on the DRS is necessarily different from the RRM measurement based on other reference signals. Therefore, the RRM measurement based on the DRS needs to be corrected and improved accordingly.